1. Field of the Invention
The present invention relates to an apparatus to be used for the mechanical and chemical-bacteriological cleaning of sandy or pebble-covered beaches.
2. Discussion of Background and Material Information
As used herein, sandy of pebble-covered beaches are the plots comprising in their major portion free rock grains, of a size varying between 0.1 and 50 mm., situated generally along seas or lakes, i.e., places which are frequented more and more by vacationers.
The considerable development of industrial and in particular touristic activities along the coasts have caused pollution phenomena to appear: undesirable deposits of waste of all sorts, including contamination of sand or pebbles by the addition of approximately 30,000 exogenous pathogenic germs to the initial natural 4,000 germs per gram which are themselves normal in the natural equilibrium or environment of the beach. Besides the adverse aesthetic aspect of such pollution, pollution also presents dangers for visitors, dangers of wounds caused by sharp objects such as broken glass, and transmission dangers of illness and disease by microbial germs which find in sand a warm and humid environment suited for their proliferation.
In an effort to combat such problems sanitation authorities, national or local, sensitized by this problem, proceed to the regular cleaning of the coasts. As to one of the more visible forms of pollution, that of wastes, there currently exist various machines for performing this work. The most simple consists of a rake fixed with respect to the chassis in the work position, which one pulls by means of a tractor and which is regularly lifted to temporarily leave the pile in place.
One type of machine suitable for this purpose conveys wastes to a receiver bin during cleaning. A first type of machine comprises a series of combs affixed to a rotating conveyer which rakes a depth of approximately 5 cm. of sand. A second type of machine comprises an attack blade positioned in front lifting a layer of sand which varies as needed from 2 to 40 cm. This sand is projected by a drum provided with small wings towards a rotating screen conveyer to be sifted there. The movement of the conveyer also causes the lifting of wastes towards the receiving container. Once the sand has been sifted it falls back to the beach.
The attention of the sanitation authorities to the problems of the pollution of the coasts by the exogenic, pathogenic microorganisms is more recent, and as a standards and methods of cleaning are still relatively poorly defined.
A first method consists of spraying a powerful disinfectant, such as solutions comprising aldehyde or phenolic compositions, which render the sand which is reached antiseptic over the sand in conventional manner. These solutions have the advantage of remaining active for a long time, such that they continue their work while the sand is stirred up by the passage of summer visitors. Unfortunately, it appears that these disinfectants also exhibit secondary effects on human beings, and on the habitat because, they prevent the non-pathogenic microorganisms which are natural for the terrain from developing.
It has, consequently, been suggested to combine the mechanical cleaning and the chemical-bacteriological cleaning into a single machine. Thus, in the apparatus disclosed in German Specification 3,209,134 the particles are first heated and then disinfected by virtue of a powerful solution comprising 5-25% lactic acid and 0.2-1% quaternary ammonium. Unfortunately, this solution can cause secondary effects such as irritations on the skin of children.
In the specification of German 3,147,648 it is mentioned that any type of disinfectant solution, even deodorizing may be used, as a complement to the mechanical sifting of the sand in this machine. No consideration is given to the secondary effects of using an overactive cleaning agent.
German Specification 3,134,522, discloses injecting into the sand a high temperature gas, such as air, through teeth of a large rake to sterilize the sand. The use of overheated air as a cleaning agent effectively destroys all of the germs even those which are indigenous and necessary for the natural equilibrium of the beach.
A second method, considered to be relatively gentle is described in French Specification 85.15284 of F-TEC Corp., in this method a sea water electrolysate is used to disinfect the sand. This electrolysate is produced either in a fixed station or in a moveable unit pulled by a tractor before being sprayed by a row of sprayers. Once the disinfection work has been performed, this electrolysate is progressively retransformed into salts contained in the sea water under the action of ultraviolet solar rays, and as a result becomes inoffensive to the tourists. However, given that during the spreading the product remains on the surface while the germs responsible for the infections are also present at several centimeters of depth, this process still remains superficial and thus ineffective.
A more careful analysis of the behavior of a liquid in a pile of sand illustrates in fact two distinct situations: the "free" liquid and that which is "bound". One understands by free liquid that which fills the empty interstices between the grains. The ratio of this empty volume over the total volume of the rock is called the porosity whose typical value for the sand is 40%. This liquid volume is useless in the disinfection process. By bound liquid, it is understood the liquid which envelopes each of the grains of sand on which the microorganisms grow, liquid which is held by surface tension. Laboratory calculations on a volume of one cubic meter of sand show that there is required 400 liters of liquid to totally soak it while 4 liters are sufficient to make it wet. Yet, when one proceeds to spreading the liquid, one unnecessarily soaks the sand.